Relative cooling power enhancement by tuning magneto-structural stability in Ni-Mn-In Heusler alloys

Abstract Off-stoichiometric Ni2MnIn Heusler alloys have drawn recent attention due to their large magnetocaloric entropy change associated with the first-order magneto-structural transition. Here we present crystal structural, calorimetric and magnetic studies of three compositions. Temperature-dependent X-ray diffraction shows clear structural transition from a 6M modulated monoclinic to a L21 cubic. A significant enhancement of relative cooling power (RCP) was achieved by tuning the magnetic and structural stability through minor compositional changes, with the measured results quantitatively close to the prediction as a function of the ratio between the martensitic transition ( T m ) temperature and austenite Curie temperature ( T C ) although the maximal magnetic induced entropy change ( Δ S m a x ) reduction is observed in the same time. The results provided an evaluation guideline of RCPs as well as magnetic-induced entropy change in designing practical active materials.